Catalytic Hydrogenation of [2.2]Paracyclophane. Unsaturated Intermediates

The catalytic hydrogenation of [2.2]paracyclophane (1) was repeated to determine whether the claim that 1 yields an octahydro[2.2]paracyclophane (2) which contains a 1,4-cyclohexadienic structural unit can be substantiated. Decahydro[2.2]paracyclophane and three isomeric dienes (I—III), as well as perhydroparacyclophane, are isolated. The NMR spectra (¹H and ¹³C) of the dienes are inconsistent with the earlier proposal, and the failure of the dienes to be aromatized by treatment with DDQ indicates that the trisubstituted double bonds reside in different six-membered rings. Computations of conformational energies aid the assignment of structures to the dienes.